In some powertrain control systems it may be desirable to disable fuel injection in some cylinders under various operating conditions. For example, a variable displacement engine control strategy may disable fuel injection and valve actuation in some cylinders at various operating ranges in order to improve fuel economy. As another example, an engine control strategy may disable fuel injection in some cylinders and operating other cylinders that are combusting a mixture of fuel and air with an increased air load (e.g. a lean burn fuel injector cut-out mode) at various operating ranges in order to improve engine efficiency and fuel economy. See, for example, U.S. Pat. No. 6,758,185.
However, the inventers herein have recognized that when air load is increased during a fuel injector cut-out mode, and fuel injectors do not stop injecting fuel as commanded, errors in torque and emissions control may be produced. Furthermore, in a variable displacement engine control strategy if cylinder valves are deactivated and fuel injectors do not stop injecting fuel as commanded, the likelihood of hydro-locking the engine may be increased.
The above issues may be addressed by, in one example, an engine comprising: at least one fuel injector sensor coupled to at least one fuel injector of a first group of cylinders; at least one fuel injector sensor coupled to at least one fuel injector of a second group of cylinders; a controller configured to operate the engine in at least a first mode and a second mode, where in the first mode the first and second cylinder groups combust air and injected fuel, where in the second mode at least one of the first and second cylinder groups combusts air and injected fuel and the other one of the first and second cylinder groups pumps air without injecting fuel; where in the first mode the controller sets a degradation condition responsive to detection of inactivity of the at least one fuel injector by the at least one fuel injection sensors; and where in the second mode the controller sets a degradation condition responsive to detection of fuel injection activity in both the first and second groups of cylinders by the fuel injection sensors, and detection of fuel injection inactivity in both the first and second groups of cylinder by the fuel injection sensors. Furthermore, in some embodiments a controller may be configured to operate the engine in a third mode, where both the first and second cylinder groups pump air without injecting fuel; and where the controller sets a degradation condition responsive to detection of fuel injection activity on either of the first and second groups of cylinders by the fuel injection sensors.
In this way cylinder group specific fuel injection activity may be verified during different modes of operation. Furthermore, fuel injector degradation may be detected and engine control may be reconfigured in order to reduce control errors and increased emissions. Additionally, in the case of a variable displacement engine detection of fuel injector degradation and changes of the engine control strategy may be used to reduce the likelihood of hydro-locking the engine.